Percent Escapes with Extent

[bwroga]

Is it possible to use percent escapes with the -extent option?

I would like to swap the width and height of an image, but keep everything else the same.

I tried all of the following:

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convert a.png -extent %hx%w d.png
convert a.png -extent '%hx%w' d.png
convert a.png -extent '%[h]x%[w]' d.png
convert a.png -extent '%[fx:h*1]x%[fx:w*1]' d.png

but I get invalid argument errors for each.

[fmw42]

Only in IM 7.

Should be OK, but system dependent whether quotes are needed and may require double quotes.

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magick a.png -extent %hx%w d.png
magick a.png -extent '%hx%w' d.png

This is not allowed syntax:

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magick a.png -extent '%[h]x%[w]' d.png

No need to multiply by 1 in this syntax:

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magick a.png -extent '%[fx:h*1]x%[fx:w*1]' d.png

[snibgo]

As Fred says, only with IM v7. Ensure you are using v7, and use "magick", not "convert".

[GeeMack]

Is it possible to use percent escapes with the -extent option?

I would like to swap the width and height of an image, but keep everything else the same.

As mentioned, the FX expressions are most versatile using IM7, but it can be done with IM6 using "-distort" and setting a viewport. Try this...

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convert a.png -set option:distort:viewport %[h]x%[w] -virtual-pixel none \
   -distort affine "%[fx:w/2],%[fx:h/2] %[fx:h/2],%[fx:w/2]" result.png

There are many options available for that virtual-pixel setting, which defines what IM does with the space not filled with any image after the distort. I used "none" which leaves a transparent background. You could use "black" or "white" or set a background color and use "-virtual-pixel background".

[bwroga]

I think I'll go ahead and upgrade, I was using 6.9.7-4. Thank you everyone.

[fmw42]

Just to be clear, GeeMack is providing an IM 6 alternative that does the same as -extent (though not as straight-forward), but using -distort Affine. In IM7 6, you can only use % escapes in a few functions including -distort, but not -extent.

[fmw42]

I think I'll go ahead and upgrade, I was using 6.9.7-4. Thank you everyone.

For differences, see https://imagemagick.org/script/porting.php#cli